1. Field of the Invention
The pre sent invention relates to a high-pressure fuel supply pump for pressurizing fuel and delivering the pressurized fuel to an high-pressure fuel supply system of an internal combustion engine, the high-pressure fuel supply pump comprising a compression chamber, a plunger reciprocating in the compression chamber for pressurizing fuel in the compression chamber, a discharge valve for discharging pressurized fuel from the compression chamber to a high-pressure fuel passage of a high-pressure fuel supply system for supplying high-pressure fuel to an internal combustion engine, and a first solenoid actuated valve for connecting and disconnecting a first low-pressure fuel passage and the compression chamber, wherein the first solenoid actuated valve is biased by a first biasing member in a closing direction of the first solenoid actuated valve, and the first solenoid actuated valve is opened or kept open against the biasing force of the first biasing member, when the first solenoid actuated valve is energized.
Also, the present invention relates to a fuel supply system for supplying fuel to an internal combustion engine, the fuel supply system comprising a high-pressure fuel supply system for supplying high-pressure fuel to the internal combustion engine, a high-pressure fuel supply pump for pressurizing fuel and delivering pressurized fuel to the high-pressure fuel supply system, and a low-pressure fuel supply system for delivering low-pressure fuel to the high-pressure fuel supply pump, wherein the high-pressure fuel supply pump comprises a compression chamber, a plunger reciprocating in the compression chamber for pressurizing fuel in the compression chamber, a discharge valve for discharging pressurized fuel from the compression chamber to a high-pressure fuel passage of the high-pressure fuel supply system, and a first solenoid actuated valve for connecting and disconnecting a first low-pressure fuel passage of the low-pressure fuel supply system and the compression chamber, wherein the first solenoid actuated valve is biased by a first biasing member in an closing direction of the first solenoid actuated valve, and the first solenoid actuated valve is opened or kept open against the biasing force of the first biasing member, when the first solenoid actuated valve is energized.
2. Description of the Related Art
The demands and requirements for reducing exhaust gas emissions of internal combustion engines, e.g. of internal combustion engines of vehicles such as cars are continuously increasing as the environmental impact of pollution becomes more and more known, and in turn, exhaust gas emissions become more and more regulated. In particular, soot emissions regulations such as for example the soot emission regulations in Europe are becoming increasingly strict.
In order to provide a technology that may meet these regulations and future regulations, fuel supply systems for supplying fuel to an internal combustion engine using a hybrid solution have been proposed which combine a low-pressure fuel supply system for supplying low-pressure fuel to an internal combustion engine and a high-pressure fuel supply system for supplying high-pressure fuel to an internal combustion engine. Such hybrid systems are configured to either supply high-pressure fuel to the internal combustion engine, e.g. via gasoline direct injection, in short referred to as GDI (sometimes also referred to as spark ignition direct injection or SIDI in short), or to supply low-pressure fuel to the internal combustion engine, e.g. via port fuel injection, in short referred to as PFI. Accordingly, such hybrid fuel supply systems may for example supply fuel either in a GDI mode or in a PFI mode, and are potential candidates to allow for meeting the strict soot emission standards and future exhaust gas regulations.
Generally, such hybrid fuel supply system may, on the one hand, benefit from the low soot emission levels which may attained with a PFI engine, and, on the other hand, benefit from the improved fuel consumption of a GDI engine.
For example, such a hybrid fuel supply system is known from EP 1 812 704 A1 which has a low-pressure fuel supply system including intake manifold injectors and a low-pressure delivery pipe and, in addition thereto, a high-pressure fuel supply system including in-cylinder injectors, a high-pressure delivery pipe and a high-pressure fuel pump. A discharge flow rate of a low-pressure fuel pump which draws fuel from a tank to the low-pressure fuel system and the high-pressure fuel supply pump of the high-pressure fuel supply pump is set based on required supply quantities to the low-pressure fuel supply system and to the high-pressure fuel supply system obtained according to the engine operation conditions. However, according to EP 1 812 704 A1, the high-pressure fuel supply pump comprises a solenoid actuated inlet valve which is a so-called “normally open” inlet valve which is open when there is no current applied to a coil of the solenoid and which is closed when a current is applied to the solenoid. Controlling an amount of fuel delivered to a high-pressure delivery pipe with such normally open solenoid actuated inlet valves has the drawback that noise and vibrations occur during operation of the high-pressure fuel pump, when high-pressure fuel is delivered to the internal combustion engine e.g. in a GDI mode of the hybrid fuel supply system and the internal combustion engine. In particular, since the fuel supply system as described in EP 1 812 704 A1 comprises the normally open solenoid actuated inlet valve, which does not require to have electric energy applied when the internal combustion engine is operated in the PFI mode by delivering low-pressure fuel to the MPI injectors, it generates the characteristic high frequency ticking noise of a “normally open” solenoid actuated valve when operating as a flow rate control valve for delivering high-pressure fuel to the internal combustion engine. Moreover, there is a limitation in pump capacity, which is quite severe for a “normally open” solenoid actuated valve.
Furthermore, regarding the general development of such hybrid fuel supply systems being configured to deliver low-pressure fuel and/or high-pressure fuel to the internal combustion engine, there are many further challenges and problems regarding the fuel delivery system to be solved. For example, one of the main challenges is to adapt a high pressure fuel delivery system for the usage in a hybrid system combined with a low-pressure fuel system e.g. for PFI operation. Namely, in such systems, the high-pressure fuel delivery system has to be adapted so that the high pressure fuel system can withstand long times of non-usage, when the internal combustion engine is mainly supplied with low pressure fuel to attain the low soot emissions.
However, for adapting a high-pressure fuel supply system to such requirements, various issues have to be considered such as efficiently controlling of a fuel flow to zero in the high-pressure fuel system, i.e. when the low-pressure fuel is to be delivered to the internal combustion engine e.g. in a PFI mode and no fuel is to be pressurized, reducing noise and vibration levels during operation of the high-pressure fuel pump, which typically occurs for “normally open” solenoid actuated valves, reduce or even prevent deterioration of fuel in the high pressure fuel system, which typically occurs due to non circulation of fresh gasoline, when low-pressure fuel is to be delivered to the internal combustion engine e.g. in PFI mode and disadvantageously further leads to a heating up of fuel in the high-pressure fuel supply system so as to additionally heat up the high-pressure fuel supply system. Further challenges relate to the occurrence of deposits at the high-pressure fuel injector e.g. due to the above-mentioned fuel deterioration and issues regarding packaging, i.e. maintaining a compact structure despite an increasing number of components.
For reducing noise and vibrations during operation in a high-pressure fuel supply pump, EP 1 701 031 A1 shows a high-pressure fuel supply pump comprising a so-called “normally closed” solenoid actuated valve which enables the supply high-pressure fuel at a sufficient flow rate at a reduced noise level and with reduced occurrence of vibrations. Here, the term “normally closed” refers to the features that the solenoid actuated inlet valve of the high-pressure fuel supply pump is generally closed, when there is no current applied to a coil of the solenoid, e.g. by biasing the valve in the direction of closing the valve by means of a biasing member such as e.g. a spring. However, when current is applied and the solenoid is energized, the valve is opened or kept open by means of the electromagnetic force generated by the energized solenoid, in contrast to the operation of the above-mentioned “normally open” solenoid actuated valves. The high-pressure fuel supply pump described in EP 1 701 031 A1 comprising the normally closed inlet valve provides sufficient high-pressure fuel flow rate at reduced noise level and reduced vibrations. However, due to its basic structure, the high-pressure fuel pump of EP 1 701 031 A1 requires solenoid control at zero fuel flow conditions, e.g. when there is no high-pressure fuel to be supplied to an internal combustion engine. However, as mentioned above, supplying low-pressure fuel e.g. in PFI mode will be the predominant mode of operation in a low-pressure/high pressure hybrid fuel supply system (e.g. GDI (SIDI)+PFI) in order to meet the low soot emission requirements. Accordingly, electric energy has to be continuously applied to the high-pressure fuel pump in order to only deliver low-pressure fuel pressure e.g. during PFI mode. Moreover, the fuel remaining inside the high-pressure fuel pump during low-pressure fuel supply by the hybrid system will heat up and may, therefore, deteriorate, which may further lead to injector deposit problems and the like.